The present invention relates to an audio-mixing apparatus and an audio-mixing processing method and more particularly, to audio-mixing apparatus and processing method for digital audio signals.
In recent years, with advancement of digital technologies, digitization of video and audio apparatus has been promoted and a mixing process in which digitized audio signals or digital audio signals as they are mixed has been widely employed even in editing of audio signals.
Conventionally, in a general method of performing the mixing process of this type of digital audio signal, pieces of serial audio data consecutively inputted from a plurality of channels are subjected to a predetermined operation process channel by channel, subjected to PCM conversion corresponding to each channel and subjected to the mixing process. Therefore, memories are provided by the same number as that of the channels and the serial audio data pieces are stored in individual channel data regions. The thus stored individual audio data pieces are subjected to the mixing process by means of a mixing processor and delivered as PCM output data pieces.
Referring to FIG. 4 showing a conventional audio-mixing apparatus in block form, the audio-mixing apparatus has an operation processor 1 for performing, channel by channel, an inverse Fast Fourier transform (FFT) process of serial input data pieces DIi representing digital audio data pieces corresponding to a plurality of channels and a PCM converter 40 for performing a PCM conversion process each in correspondence to operation data pieces PDi of respective channels and delivering PCM conversion data pieces DCi. There is further provided a plurality of memories 30 for storing the individual PCM conversion data pieces DCi of the respective channels, and a mixing processor 20 for performing a mixing process of the PCM conversion data pieces MCi of the respective channels read out of the memories 30 and generating PCM output data pieces DOi.
The operation of the conventional audio-mixing apparatus will be described with reference to FIG. 4. The operation processor 1 is supplied with serial input data pieces DIi of a plurality of channels via an input terminal TI, performs an operation process such as an inverse FFT process channel by channel to generate operation data pieces PDi corresponding to the respective channels and applies the operation data pieces PDi to the PCM converter 40.
In the PCM converter 40, a PCM conversion process corresponding to each channel is carried out in response to the supply of each of the operation data pieces PDi to deliver, channel by channel, PCM conversion data pieces DCi which in turn are supplied to the respective memories 30. Each of the PCM conversion data DCi supplied to each memory 30 is temporarily stored therein for preparation for the mixing process.
The mixing processor 20 reads PCM conversion data pieces MCi of the respective channels out of the respective memories 30, performs the mixing processing of the read-out PCM conversion data pieces and generates consecutive PCM output data pieces DOi of the respective channels which in turn are delivered via an output terminal TO. At that time, the mixing processor 20 does not operate before all of the memories 30 have completed storage of the PCM conversion data pieces DCi which are obtained by subjecting all of the serial input data pieces DIi of the plurality of channels to the operation process and subjecting the operated input data pieces to the PCM conversion.
According to the aforementioned conventional audio-mixing apparatus and processing method, in the mixing process of digital audio signals of the plurality of channels, the data pieces of the respective channels are separately subjected to the PCM process and PCM output data pieces are generated by combining necessary signal data pieces and mixing them. Therefore, the mixing process is carried out after completion of operation execution for all channels and completion of storage of operation data pieces regardless of whether or not the mixing process for all of the plurality of channels is necessary, leading to disadvantages that as the number of channels increases, the operation time increases and the capacity of memories for operation data storage increases.